Implementation of SQLExceptionTranslator that uses
Oracle vendor code, as included in the ORA-nnn methods. More precise than SQLState implementation,
but Oracle-specific. The JdbcTemplate class enables error handling
to be parameterized without making application's dependent
on a particular RDBMS.
****TODO: this class should handle a much wider range of
Oracle error codes. This can easily be done by adding additional
values to the switch.